1. Field of the Invention
The present invention relates to a printed circuit board and a motor drive having the printed circuit board, and in particular relates to a printed circuit board having the function of detecting a deterioration in components and the like mounted on the printed circuit board owing to a water-soluble or water-insoluble cutting fluid or the like, and a motor drive having the printed circuit board.
2. Description of Related Art
Printed circuit boards and components mounted on the printed circuit boards are contaminated with time by dust or machining fluids such as water-soluble or water-insoluble cutting fluids or grinding fluids (hereinafter also called “water-soluble or water-insoluble cutting fluid or the like” or “electrolytic solution”), and may have operation malfunctions. For example, when conductive foreign matter such as a cutting fluid or swarf adheres between pins of an IC chip mounted on a printed circuit board, the foreign matter may reduce the insulation resistance between the pins and cause an electrical malfunction. If the adhering foreign matter is corrodible, the foreign matter may break a conductive pattern of the printed circuit board and cause a malfunction.
With miniaturization of electronic components in recent years, the components have been mounted more densely and printed circuit boards have had finer and denser patterns. In such printed circuit boards, external environmental factors, more specifically, water-soluble cutting fluids may cause corrosion in the wiring patterns of the printed circuit boards or malfunctions in the components with a lapse of time.
Thus, methods for detecting a deterioration in a printed circuit board owing to external environmental factors including corrodible gases, dust, and the like are proposed (for example, Japanese Unexamined Patent Publication (Kokai) No. 10-62476, hereinafter referred to as “Patent Literature 1”). Patent Literature 1 discloses a deterioration detection device of a printed circuit board for electronic equipment. The deterioration detection device includes deterioration detection traces and a deterioration determining and warning means. The deterioration detection traces having a predetermined conductor width are provided on the printed circuit board so as to be exposed to atmosphere. The deterioration detection traces are each energized with a predetermined voltage from a power supply at a predetermined impedance. The deterioration determining and warning means detects a trace voltage that is a voltage between predetermined two points distant in a longitudinal direction of the trace at predetermined time intervals, and obtains data that indicates at least the narrowness of the trace from detection data of the pattern voltage. The deterioration determining and warning means outputs a warning signal, when the data indicating the narrowness exceeds one threshold value or each of a plurality of threshold values. As described above, the invention described in Patent Literature 1 detects deterioration in the printed circuit board from an increase in the impedance of the deterioration detection trace that has been narrowed owing to corrosion, by measuring a voltage across the deterioration detection trace provided on the printed circuit board.
However, the conventional art described in Patent Literature 1 is intended not for water-soluble or water-insoluble cutting fluids but mainly for corrodible gases. Also, the conventional art does not have a mechanism for storing fluid materials such as water-soluble or water-insoluble cutting fluids, and therefore causes deteriorations to proceed concurrently in other components and wiring traces.